Hydraulic pole jack

ABSTRACT

The hydraulic jack has a pole gripping attachment with a swivel chain attachment means operable in a slot therein to provide for chain tightening with minimum piston movement and little or no eccentric loading of the piston. The cylinder is of single acting design with dual tandem spring return. High hydraulic pressure (over 6,000 PSI) is used to facilitate light weight and compact design features.

[ NOV. 20, 1973 United States Patent [191 Thiermann ER 3 1 24 .5 2 .wHun 3 HD 03 02 99 ll 73 15 09 45 56 1 im 6W m mu mm n d K ra k MhR J .8EE& L ma 0 aw Pmw ww I L U n A o R t D n 8 Y v Hm 4 6 5 7 PrimaryExaminer-Othell M. Simpson Assistant Examiner-Robert C. Watson [22]Filed: Jan. 10, 1972 Attorney-Andrus, Sceales, Starke & Sawall [21]Appl. No.: 216,578

[57] ABSTRACT The hydraulic jack has a pole'gripping attachment with aswivel chain attachment means operable in a E2lb 19/00 254/30, 131, 133,

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slot therein to provide for chain tightening with minimum pistonmovement and little or no eccentric load- [56] References Cited ing ofthe piston. The cylinder is of single acting de- UNITED STATES PATENTSsign with dual tandem spring return. High hydraulic pressure (over 6,000PS1) is used to facilitate light weight and compact design features.

254/ 133 254/30 254/93 R 5 Claims, 7 Drawing Figures t n.1,. mam e m mmEBG 049 76 999 111 //l 2 2 111 928 978 853 452 7 v 33 PAIENTED NOV 20I975 SHFFT 2 CF 2 HYDRAULIC POLE JACK BACKGROUND OF THE INVENTION Thisinvention relates to hydraulic pole jacks or pullers of the general typeemployed in lifting poles or posts, usually wooden, vertically fromtheir set position in the ground, as when it is desired to remove thesame from the ground.

In the construction of jacks for this purpose it is generally desirableto provide a compact unit for ready portability either as a whole or indisassembled pieces, which gives sufficient lift to remove the polewithout the need to dig out the butt. Digging out a pole butt (as thepart of the pole in the earth is called) is very time consuming if doneby hand as is often required; for many pole locations are inacessible tomachines.

The pole jacks heretofore employed, use low pressure hydraulics, have anon-swiveling or non-floating chain hookup, and have no feature totighten the chain prior to and during start of the lift. This results inconsiderable loss of effective lift per stroke due to chain slippage upthe pole before blighting in, the use of larger heavier cylinders andpistons due to low hydraulic pressure and eccentric loading of pistonand the use of a heavier chain due to poor chain hookup.

SUMMARY OF THE INVENTION According to the present invention the chainwhich wraps around the pole has its ends secured in corresponding swivelmembers constituting trunnions on opposite sides of a tubular body thatfits over the power cylinder and rests on a flange or upwardly facingshoulder on the cylinder.

A pole gripping attachment of generally U shape in plan view receivesthe tubular body between its sides and the latter have generallyvertical slots therein through which the swivel trunnions extend,thereby mounting the attachment for limited floating vertically relativeto the tubular body.

The back of the attachment is positioned to face the pole and has treadmeans thereon to grip the surface of the pole during lifting.

The slots in the sides of the channel shaped attachment are inclinedoutwardly from the pole tread to facilitate tightening of the chainprior to lifting.

For the purpose of providing more rapid return of the cylinderdownwardly upon the piston following release of pressure from the powerfluid, the piston is constructed as a hollow plunger facing upwardlyinto the cylinder and a plurality of concentric coil springs aredisposed within the piston with an equalizer member effecting tandemactuation of the springs in compression as the cylinder is raised on theplunger-like piston.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings illustratethe best mode presently contemplated for carrying out the invention.

In the drawings:

FIG. 1 is a perspective view of the pole jack in operative position forlifting a pole;

FIG. 2 is an exploded side elevation of the jack;

FIG. 3 is an axial section of the power cylinder showing the returnspring construction with the cylinder and piston collapsed;

FIG. 4 is a view similar to FIG. 3 with the cylinder and piston extendedas immediately following a pole lift operation;

FIG. 5 is a detail side elevational view showing the jack as initiallyinstalled adjacent a pole and the chain manually assembled therewith;

FIG. 6 is a view similar to FIG. 5 showing the attachment dropped downto effect initial tightening of the chain prior to operation of thepower lift cylinder; and

FIG. 7 is a view similar to FIG. 6 showing the jack after operation ofthe cylinder and with the pole lifted a distance generally correspondingto the movement of the cylinder.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 of thedrawing the jack 1 is positioned on the base 2 adjacent to the pole 3for lifting of the latter.

A hydraulic pump and control unit 4 is removably connected by a flexiblehose 5 to the upper end of power cylinder 6 of jack 1.

A chain 7 is wrapped around the back side of pole 3 and has its oppositeend portions secured in corresponding trunnion-like swivel members 8 onopposite sides of the cylinder 6.

The swivel members 8 may be mounted directly on cylinder 6, butpreferably constitute trunnions on the opposite sides of a tubularsleeve-like body 9 which removably slips over the top of the cylinderand rests upon a flange-like upwardly facing shoulder 10 extendingcircumferentially of the cylinder.

Each swivel member 8 carries a chain hook ll pivoted thereto and havinga slotted recess 12 therein for receiving a selected link 13 of a polegripping chain 7. The construction is such that the chain may bemanually adjusted about the pole to a maximum tightness, leaving thechain links at the loose ends of the chain free to hang down from hook11 without interfering with the operation of the jack.

A generally U-shaped or channel swivel attachment 14 has its side plates15 swiveled on the trunnion members 8 and its back 16 provided withgripping prongs 17 to engage the pole 3.

Each side plate 15 of attachment 14 has a slot 18 receiving thecorresponding trunnion 8 and permitting limited vertical movement ofattachment 14 relative to cylinder 6.

The slots 18 are generally vertical with an outwardly inclined directionaway from the pole engaging back 16, to provide for an initial take-upof slack in the chain 7 by manually moving the cylinder away from thepole and letting the attachment 14 drop relative to the trunnions 8whereupon the slight incline of the slots 18 will effect a preliminarytightening of the chain and slant the cylinder away from the pole readyfor a lifting operation.

The hose 5 from the pump and control unit 4 is next coupled to the topend of cylinder 6 by quick connection coupling 19 to complete assemblyof the jack ready for operation.

In this assembly the cylinder 6 is inverted upon a vertically disposedplunger-like hollow piston 20 which is pivotally supported on base 2.

Upon admission of pressure fluid to the cylinder 6 through hose 5 fromunit 4 the cylinder is lifted vertically on the piston 20 until a stop21 disposed internally of the lower edge of the skirt portion ofcylinder 6 engages a stop rim 22 at the upper end edge of the piston 20,whereupon further lifting movement of cylinder 6 is stopped.

If the pole 3 needs further lifting beyond a single stroke of cylinder6, it is possible to secure the pole at its initial lifted position,then release the fluid pressure in cylinder 6 and drop the cylinder to apoint where the chain 13 is loosened and can be disconnected.

After this the chain and jack are re-assembled with a grip on the polelower down from the first grip and the pole is again and further liftedby actuation of the cylinder as previously described. In like manner thelifting can involve as many successive lifting steps as may be needed.

Where a liquid is utilized for the power fluid reliance solely upon theweight of cylinder 6 to force the liquid from the cylinder for returningthe latter to a start position following a lifting operation generallyinvolves too long a time.

In order to shorten the return time for cylinder 6 spring means areprovided within the hollow piston to encourage the downward pistonmovement.

For this purpose, and in order to provide for the full operative strokeof the cylinder 6 upon piston 20, two concentrically disposed coilsprings 23 and 24 are operatively arranged in tandem by providing afloating equalizing member 25 therebetween.

In the embodiment illustrated in FIG. 3 the inner coil spring 23 isconcentrically disposed longitudinally of a center post 26 dependingfrom the top 27 of cylinder 6 into the hollow piston 20 forapproximately the full length of the cylinder as represented by thestroke of the cylinder, and which has a circumferential flange 28 at itslower end which supports the spring.

The upper end of inner spring 23 engages an inner upper flange 29 on theupper end of sleeve-like equalizing member 25 to support the latter.

The member 25 is shown as a sleeve containing the inner spring 23 andabout which the outer spring 24 is disposed, and the post 26, spring 23,sleeve member 25 and spring 24 all have a length generally correspondingto the length of the space between the top 27 of the cylinder and thebottom head 30 within the hollow plunger-like piston 20.

The floating equalizer sleeve member 25 has an outer circumferentialflange 31 at its lower end supporting outer coil spring 24.

The upper end of coil spring 24 presses against an inner flange 32 onthe upper end edge of piston 20.

The center post 26 is tubular and closed at the bottom by the flangehead 28, and is provided with lateral holes 33 therein for free flow ofpower fluid from coupling 19 into and out of the cylinder 6. Similarholes may be provided in member 25.

A suitable circumferential seal 34 is provided between the inner surfaceof cylinder 6 and the outer surface of the plunger or piston 20 near theupper end of the latter.

Various modes of carrying out the invention are contemplated as beingwithin the scope of the following claims particularly pointing out anddistinctly claiming the subject matter which is regarded as theinvention.

I claim: i

1. A hydraulic pole jack comprising a power cylinder adapted to bedisposed adjacent to a pole and substantially parallel thereto with oneelement of the power cylinder fixedly supported, a chain adapted to wraparound the pole with its opposite end portions secured to the movableelement of said power cylinder, swivel means having opposed alignedtumnions carried by the movable element of said power cylinder onopposite sides thereof, and means pivotally secured to each trunnion ona transverse axis with respect thereto and adjustably receiving thecorresponding end portions of said chain.

2. The jack of claim 1, and a sleeve member carrying said trunnions andadapted to slip over the upper end of said power cylinder, and abutmentmeans on the movable element of said power cylinder to support saidsleeve member.

3. The construction of claim 2 and pole gripping means mounted on saidtrunnions and comprising a channel member with its back adapted toengage the pole and with means in each side wall thereof adapted toreceive said trunnions to provide for pivoting of said gripping meansrelative to said power cylinder generally upon the axis of saidtrunnions to substantially reduce any eccentric loading of the piston asit is extended.

4. The construction of claim 3 in which a slot is provided in each sidewall of said gripping means and through which the corresponding trunnionextends, said slots providing for limited vertical movement of saidgripping means relative to said power cylinder to increase the tightnessof said chain upon the pole generally prior to actuation of said powercylinder and during initial actuation of the cylinder.

5. The construction of claim 4 in which said slots are inclined awayfrom the back of said gripping means to more effectively tighten saidchain upon the pole as said gripping means drops relative to the pole.

1. A hydraulic pole jack comprising a power cylinder adapted to bedisposed adjacent to a pole and substantially parallel thereto with oneelement of the power cylinder fixedly supported, a chain adapted to wraparound the pole with its opposite end portions secured to the movableelement of said power cylinder, swivel means having opposed alignedturnnions carried by the movable element of said power cylinder onopposite sides thereof, and means pivotally secured to each trunnion ona transverse axis with respect thereto and adjustably receiving thecorresponding end portions of said chain.
 2. The jack of claim 1, and asleeve member carrying said trunnions and adapted to slip over the upperend of said power cylinder, and abutment means on the movable element ofsaid power cylinder to support said sleeve member.
 3. The constructionof claim 2 and pole gripping means mounted on said trunnions andcomprising a channel member with its back adapted to engage the pole andwith means in each side wall thereof adapted to receive said trunnionsto provide for pivoting of said gripping means relative to said powercylinder generally upon the axis of said trunnions to substantiallyreduce any eccentric loading of the piston as it is extended.
 4. Theconstruction of claim 3 in which a slot is provided in each side wall ofsaid gripping means and through which the corresponding trunnionextends, said slots providing for limited vertical movement of saidgripping means relative to said power cylinder to increase the tightnessof said chain upon the pole generally prior to actuation of said powercylinder and during initial actuation of the cylinder.
 5. Theconstruction of claim 4 in which said slots are inclined away from theback of saId gripping means to more effectively tighten said chain uponthe pole as said gripping means drops relative to the pole.